1. Field of the Invention
The present invention generally relates to a technology generically referred to as a micro-reactor and a micro-chemical process for controlling a fluid with a flow passage structure of several micrometers to several millimeters to stably realize a chemical engineering unit operation or an analysis within a short period of time. More particularly, the present invention relates to a microscopic flow passage structure, a microscopic liquid droplet generating method, a microscopic liquid droplet generating system, particles, and microcapsules.
The present invention can be applied to particles, particle dispersions and manufacturing methods thereof used for image display elements (polymerized toner, microcapsules used for cataphoresis type paperlike displays), emulsions used for drug delivery, coating, cosmetics, other emulsions, and photoconductive materials.
2. Description of the Related Art
Particles obtained by solidifying emulsions or dispersed phases in emulsions and capsule particles obtained by solidifying liquid droplet surfaces are used for various industrial purposes.
Presently, the following methods are used for industrial production of emulsified dispersions.
(1) Patent Document 1, etc., discloses a method of emulsification by a homogenizer.
(2) Patent Document 2, etc., discloses a method of ultrasonic emulsification.
The technologies of (1) and (2) are used for obtaining an emulsified dispersion from a substance. The substance to be dispersed into particles corresponds to a dispersed phase, and the dispersed phase is injected into a continuous phase. Shear force is repeatedly applied to the dispersed phase with mechanical actions. However, the shear force applied to the dispersed phase is inconsistent according to the emulsifying position, and therefore, the resultant particles become polydispersive (i.e., having inconsistent sizes).
(3). Patent Document 3, etc., discloses a method of emulsification by using a porous glass film. Conversely, in the method of (3), the dispersed phase and the continuous phase are partitioned with a porous glass film, the dispersed phase is pushed against the continuous phase so that the dispersed phase passes through the porous glass film and contacts the continuous phase, surface tension serves as the shear force, and the dispersed phase is finally turned into particles, thereby obtaining an emulsified dispersion.
However, sizes of the generated particles are affected by inconsistencies in the pore sizes, and therefore, the resultant particles become polydispersive.
There is a method of manufacturing highly monodispersive emulsified dispersions and particles as follows.
(4) Patent Document 4, etc., discloses a method of micro-channel emulsification.
A film for dividing a dispersed phase and a continuous phase is artificially made to have a uniform structure. Therefore, considerably monodispersive particles can be obtained, where the standard deviation of diameters of particles/average diameter of particles is 0.03 or less. However, the sizes of the channels are smaller than the desired particle size. Therefore, when a liquid including particles is used as the dispersed phase, the channels may be clogged.
(5) Patent Document 5 discloses a method of generating monodispersive micro liquid droplets by using plural Y-type microchannels. However, it is difficult to form multiple flow passages and to guide the same amount of fluid into all of the flow passages. Further, the number of liquid droplets generated from one channel per one unit of time is several thousand, and therefore, yielding ability is low.
(6) Patent Document 6 discloses a method of manufacturing toner by membrane emulsification.    Patent Document 1: Japanese Patent No. 3476223    Patent Document 2: Japanese Patent No. 3218445    Patent Document 3: Japanese Patent No. 2733729    Patent Document 4: Japanese Laid-Open Patent Application No. 2000-273188    Patent Document 5: Japanese Laid-Open Patent Application No. 2004-358386    Patent Document 6: Japanese Laid-Open Patent Application No. H7-120974    Patent Document 7: Japanese Patent No. 3511238    Patent Document 8: Japanese Patent No. 3635575    Patent Document 9: Japanese Laid-Open Patent Application No. 2004-243308    Patent Document 10: Japanese Laid-Open Patent Application No. 2004-197083    Patent Document 11: Japanese Laid-Open Patent Application No. 2005-185877    Patent Document 12: Japanese Laid-Open Patent Application No. 2005-213334    Patent Document 13: Japanese Laid-Open Patent Application No. 2005-238118    Patent Document 14: Japanese Laid-Open Patent Application No. 2004-098225    Non-patent literature 1: Rayleigh, Lord “On the Instability of Jets” Proc. London Math. Soc. 110:4 [1878]    Non-patent literature 2: Schneider J. M., C. D. Hendricks, Rev. Instrum. 35 (10), 1349-50 [1964]    Non-patent literature 3: Lindblad N. R. and J. M. Schneider, J. Sci. Instrum. 42, 635 [1965]